Dynamic shift control for an automatic transmission

ABSTRACT

An improved control, which dynamically adjusts the shift control parameters in response to an indication of the driving style of the vehicle operator. The driving style indication is used to form a dynamic shift factor DSF, which is used to ratiometrically schedule the shift pattern, line pressure and desired shift time between predefined Normal and Performance values to provide a shift control parameter uniquely suited to the driving style of the operator of the vehicle.

This is a Continuation-in-Part of U.S. Ser. No. 07/776,030, filed Oct.15, 1991, now U.S. Pat. No. 5,152,192 issued on Oct. 6, 1992.

This invention relates to a control of shift timing and pressure in amotor vehicle automatic transmission, and more particularly, to acontrol which varies in relation to the manner in which the vehicle isdriven.

BACKGROUND OF THE INVENTION

Automatic transmissions of the type addressed by this invention, includegear elements for defining several different forward speed ratiosbetween input and output shafts of the transmission, andelectrohydraulic controls for shifting among the various ratios inrelation to vehicle speed and load indications. The shifting is effectedwith a number of fluid operated torque transmitting devices, referred toherein as clutches, which the controls engage and disengage according toa predefined pattern to establish a desired speed ratio.

The various speed ratios of the transmission are typically defined interms of the ratio Ni/No, where Ni is the input shaft speed and No isthe output shaft speed. Speed ratios having a relatively high numericalvalue provide a relatively low output speed and are generally referredto as lower speed ratios; speed ratios having a relatively low numericalvalue provide a relatively high output speed and are generally referredto as upper speed ratios. Accordingly, shifts from a given speed ratioto a lower speed ratio are referred to as downshifts, while shifts froma given speed ratio to a higher speed ratio are referred to as upshifts.

A first aspect of shift control is shift scheduling, also known as shiftpattern generation. This function is generally carried out by comparingspecified vehicle operating parameters (speed and load) to predefinedthresholds to determine when shifting is appropriate. Multiple sets ofpredefined thresholds may be used in connection with a driver preference(Normal/Performance) switch, or control logic which infers the drivingstyle of the operator.

A second aspect of shifting is fluid pressure control. In mosttransmissions having electrohydraulic controls, the fluid pressureoutput of a driven pump is regulated to a scheduled pressure (linepressure) and then distributed to the various clutches of thetransmission via electrically operated shift valves and timing devicessuch as hydraulic accumulators. The scheduled pressure is generallyspeed and load (torque) dependent, and operates not only to maintainadequate torque capacity in engaged clutches, but to control clutchengagement rate during shifting. Since the clutch engagement rateaffects shift feel, certain transmission controls increase the normallyscheduled pressure, at least during shifting, when a sporty orperformance shift feel is desired.

In most transmission pressure controls, an adaptive trim or correctionof the scheduled pressure can be employed as a means of compensating forvariability associated with part-to-part tolerances, wear, etc. One suchcontrol, set forth in the U.S. Pat. No. 4,283,970 to Vukovich, issuedAug. 18, 1981, and assigned to the assignee of the present invention,develops an adaptive correction of the scheduled line pressure based ona deviation of the actual shift time from a desired shift timecharacteristic of high quality shift feel. In such a system, alternatedesired shift time schedules may also have to be employed, depending onwhether Normal or Performance pressures are selected.

SUMMARY OF THE PRESENT INVENTION

The present invention is directed to an improved shift control whichdynamically adjusts the shift control parameters in response to anindication of the driving style of the vehicle operator. The drivingstyle indication is used to form a dynamic shift factor DSF, which isused to ratiometrically schedule the shift pattern, line pressure anddesired shift time between predefined values corresponding to diversemodes of operation, referred to herein as Normal and Performance. Thisprovides a continuum of shift control parameters uniquely suited to thedriving style of the operator of the vehicle.

In the illustrated embodiment, the driving style indication is based ona measure of the average peak acceleration during specified operation ofthe vehicle. To determine the average peak acceleration, thelongitudinal acceleration of the vehicle is continuously determined inthe course of vehicle operation. The peak or maximum acceleration valuesoccurring in successive ratio-dependent time intervals are identifiedand accumulated to form cumulative and average peak acceleration terms,ACCSUM and AVPACC.

The ratio-dependency of the time intervals over which the peakacceleration values are identified causes a faster updating of theaverage peak acceleration AVPACC, and hence the dynamic shift factorDSF, in the lower ratios. This reflects an underlying recognition thatthe peak acceleration observed in the lower ratios provides a morereliable indication of the driver preference than that observed inhigher ratios. To this end, the acceleration time interval increaseswith increasing ratio, with little or no accumulation in the higherratios.

A differential gain in the accumulation of peak acceleration may beemployed to bias the shift parameter schedules toward the Normal orPerformance levels. In the illustrated embodiment, the control is biasedtoward the Performance mode schedule by accumulating peak accelerationvalues in excess of the average peak acceleration at a higher gain thanpeak acceleration values below the average peak acceleration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a-1b form a schematic diagram of a five-speed automatictransmission controlled in accordance with this invention by acomputer-based control unit.

FIG. 2 is a state diagram for the clutches of the transmission depictedin FIGS. 1a-1b.

FIG. 3 is a chart depicting the electrical state changes required forshifting from one speed ratio to another.

FIGS. 4a-4b graphically depict normal and performance shift patterns.

FIG. 5 graphically depicts the identification of peak accelerationvalues over a period of time.

FIG. 6 graphically depicts the dynamic shift factor DSF as a function ofthe average peak acceleration AVPACC.

FIG. 7 graphically depicts the accumulation of peak acceleration values.

FIGS. 8, 9a-9b and 10-12 depict flow diagrams representative of computerprogram instructions executed by the control unit of FIG. 1a in carryingout the control of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1a-1b of the drawings, the reference numeral 10generally designates a motor vehicle drivetrain including an engine 12and a planetary transmission 14 having a reverse speed ratio and fiveforward speed ratios. Engine 12 includes a throttle mechanism 16mechanically connected to an operator manipulated device, such as anaccelerator pedal (not shown), for regulating the air intake of theengine. The engine 12 is fueled by a conventional method in relation tothe air intake to produce output torque in proportion thereto. Suchtorque is applied to the transmission 14 through the engine output shaft18. The transmission 14, in turn, transmits engine output torque to anoutput shaft 20 through a torque converter 24 and one or more of thefluid operated clutches C1-C5, OC, Reverse clutch CR, and one-wayclutches 26-30, such clutches being applied or released according to apredetermined schedule for establishing a desired transmission speedratio.

Referring now more particularly to the transmission 14, the impeller orinput member 36 of the torque converter 24 is connected to be rotatablydriven by the output shaft 18 of engine 12 through the input shell 38.The turbine or output member 40 of the torque converter 24 is rotatablydriven by the impeller 36 by means of fluid transfer therebetween and isconnected to rotatably drive the turbine shaft 42. A stator member 44redirects the fluid which couples the impeller 36 to the turbine 40, thestator being connected through a one-way device 46 to the housing oftransmission 14.

The torque converter 24 also includes a clutch TCC comprising a clutchplate 50 secured to the turbine shaft 42. The clutch plate 50 has afriction surface 52 formed thereon adaptable to be engaged with theinner surface of the input shell 38 to form a direct mechanical drivebetween the engine output shaft 18 and the turbine shaft 42. The clutchplate 50 divides the space between input shell 38 and the turbine 40into two fluid chambers: an apply chamber 54 and a release chamber 56.

When the fluid pressure in the apply chamber 54 exceeds that in therelease chamber 56, the friction surface 52 of clutch plate 50 is movedinto engagement with the input shell 38, thereby engaging the TCC toprovide a mechanical drive connection in parallel with the torqueconverter 24. In such case, there is no slippage between the impeller 36and the turbine 40. When the fluid pressure in the release chamber 56exceeds that in the apply chamber 54, the friction surface 52 of theclutch plate 50 is moved out of engagement with the input shell 38, asshown in FIG. 1a, thereby uncoupling such mechanical drive connectionand permitting slippage between the impeller 36 and the turbine 40.

The turbine shaft 42 is connected as an input to the carrier Cf of aforward planetary gearset f. The sun Sf is connected to carrier Cf viathe parallel combination of one-way clutch F5 and friction clutch OC.The clutch C5 is selectively engageable to ground the sun Sf. The ringRf is connected as an input to the sun S1r of a compound rearwardplanetary gearset r via the parallel combination of one-way clutch Fland friction clutch C3. The clutch C2 selectively connects the forwardgearset ring Rf to rearward gearset ring Rr, and the Reverse clutch CR.selectively grounds the ring Rr. The sun S2r is selectively grounded byclutch C4 or by clutch C1 through the one-way clutch F2. The pinioncarrier Cr mechanically couples the pinion gears P1r, P2r and isconnected as an output to shaft 20.

The various speed ratios and the clutch states required to establishthem are set forth in the chart of FIG. 2. Referring to that Figure, itis seen that the Park/Neutral condition is established by releasing allof the clutches with the exception of clutch OC. A garage shift toReverse is effected by engaging the C3 and OC clutches. In the forwardspeed ranges, a garage shift to 1st is effected by engaging the clutchesC1 and C4. In this case, the forward gearset f is locked up and theone-way clutch Fl applies the turbine speed Nt as an input to the sunelement Sr of rearward gearset r, providing a Ni/No ratio of 3.61.

As the vehicle speed increases, an upshift from 1st to 2nd is effectedsimply by engaging clutch C2; the one-way clutch Fl overruns as soon ason-coming clutch C2 develops sufficient torque capacity. The forwardgearset f remains locked up, and the clutch C2 applies the turbine speedNt as an input to the ring element Rr of rearward gearset r to provide aNi/No ratio of 1.85. Downshifting from 2nd to 1st merely involvesreleasing clutch C2.

The upshift from 2nd to 3rd is effected by engaging clutch C5 andreleasing clutch OC so that the forward gearset operates as anoverdrive, thereby providing a Ni/No ratio of 1.37. Downshifting from3rd to 2nd is effected by releasing clutch C5 and engaging clutch OC toreturn the forward gearset f to a lock-up condition.

The upshift from 3rd and 4th is effected by releasing clutch C5 andengaging clutch OC to return the forward gearset f to a lock-upcondition, while releasing clutch C4 and engaging clutch C3 to lock-upthe rearward gearset r, one-way clutch F2 releasing the rear planet axisPr. In this case, the turbine speed Nt is transmitted directly to outputshaft 20 for a Ni/No ratio of 1.00. The downshift 4th to 3rd is effectedby releasing clutch OC and engaging clutch C5 to return the forwardgearset f to an overdrive condition, while releasing clutch C3 andengaging clutch C4 to apply the turbine speed Nt as an input to the ringelement Rr.

Completing the shift analysis, the upshift from 4th to 5th is effectedby engaging clutch C5 (and releasing clutch OC if engine braking isselected) to operate the forward gearset f in an overdrive condition,thereby providing a Ni/No ratio of 0.74. Downshifting from 5th to 4th iseffected by releasing clutch C5 (and engaging clutch OC if enginebraking is selected).

A positive displacement hydraulic pump 60 is mechanically driven by theengine output shaft 1B. Pump 60 receives hydraulic fluid at low pressurefrom the fluid reservoir 64 and filter 65, and supplies line pressurefluid to the transmission control elements via output line 66. Apressure regulator valve (PRV) 68 is connected to the pump output line66 and serves to regulate the line pressure by returning a controlledportion of the line pressure to reservoir 64 via the line 70. The PRV 68is biased at one end by orificed line pressure in line 71 and at theother end by the combination of a spring force, a Reverse ratio fluidpressure in line 72 and a controlled bias pressure in line 74.

The Reverse fluid pressure is supplied by a Manual Valve 76, describedbelow. The controlled bias pressure is supplied by a Line Pressure BiasValve 78 which develops pressure in relation to the current supplied toelectric force motor 80. Line pressure is supplied as an input to valve78 via line 82, a pressure limiting valve 84 and filter 85. The limitedline pressure, referred to as ACT FEED pressure, is also supplied as aninput to other electrically operated actuators of the control system vialine 86. With the above-described valving arrangement, it will be seenthat the line pressure of the transmission is electrically regulated byforce motor 80.

In addition to regulating line pressure, the PRV 68 develops a regulatedconverter feed (CF) pressure for the torque converter 24 in line 88. TheCF pressure is supplied as an input to TCC Control Valve 90, which inturn directs the CF pressure to the release chamber 56 of torqueconverter 24 via line 92 when open converter operation is desired. Inthis case, the return fluid from torque converter 24 is exhausted vialine 94, the TCC Control Valve 90, an oil cooler 96 and an orifice 98.When closed converter operation is desired, the TCC Control Valve 90exhausts the release chamber 56 of torque converter 24 to an orificedexhaust 100, and supplies a regulated TCC apply pressure in line 102 tothe apply chamber 54, thereby engaging the TCC. The TCC apply pressurein line 102 is developed from line pressure by a TCC Regulator Valve104.

Both the TCC Control Valve 90 and the TCC Regulator Valve 104 are springbiased to effect the open converter condition, and in each case, thespring force is opposed by an electrically developed control pressure inline 106. The control pressure in line 106 is developed by the solenoidoperated TCC Bias Valve 108, through a ratiometric regulation of thefluid pressure in line 110. When closed converter operation is desired,the solenoid of TCC Bias Valve 108 is pulse-width-modulated at acontrolled duty cycle to ramp up the bias pressure in line 106. Biaspressures above the pressure required to shift the TCC Control Valve tothe closed-converter state are used to control the TCC apply pressuredeveloped in line 102 by TCC Regulator Valve 104. In this way, the TCCBias Valve 108 is used to control the torque capacity of the TCC whenclosed converter operation is desired.

The friction clutches C1-C5, OC and CR are activated by conventionalfluid operated pistons P1-P5, POC and PCR, respectively. The pistons inturn, are connected to a fluid supply system comprising the Manual Valve76 referred to above, the Shift Valves 120, 122 and 124, and theAccumulators 126, 128 and 130. The Manual Valve 76 develops supplypressures for Reverse (REV) and the various forward ranges (DR, D32) inresponse to driver positioning of the transmission range selector 77.The REV, DR and D32 pressures, in turn, are supplied via lines 72, 132and 134 to the various Shift Valves 120-124 for application to the fluidoperated pistons P1-P5, POC and PCR. The Shift Valves 120, 122 and 124are each spring biased against controlled bias pressures, the controlledbias pressures being developed by the solenoid operated valves A, C andB. The accumulators 126, 128 and 130 are used to cushion the apply, andin some cases the release, of clutches C5, C2 and C3, respectively.

A chart of the ON/OFF states of valves A, C and B for establishing thevarious transmission speed ratios is given in FIG. 3. In Neutral andPark, the solenoids A, B and C are all off. In this condition, linepressure is supplied to clutch piston POC through orifice 176, but theremaining clutches are all disengaged. Reverse fluid pressure, whengenerated by Manual Valve 76 in response to driver displacement of rangeselector 77, is supplied directly to clutch piston P3 via lines 72, 73and 140, and to clutch piston PCR via lines 72, 142, orifice 144 andShift Valve 124.

A garage shift to the forward (Drive) ranges is effected when ManualValve 76 is moved to the D position, connecting line pressure to the DRpressure supply line 132. The DR pressure is supplied to the clutchpiston Pl via line 146 and orifice 148 to progressively engage clutchC1. At the same time, Solenoid Operated Valves A and C are energized toactuate Shift Valves 120 and 122. The Shift Valve 122 directs DRpressure in line 132 to clutch piston P4 via Regulator Valve 150 andline 152. The Shift Valve 120 supplies a bias pressure to the RegulatorValve 150 via line 154 to boost the C4 pressure. In this way, clutchesC1, C4 and OC are engaged to establish 1st speed ratio.

Referring to the chart of FIG. 3, a 1-2 upshift is effected bydeenergizing Solenoid Operated Valve A to return Shift Valve 120 to itsdefault state. This routes DR pressure in line 132 to the clutch pistonP2 via Shift Valve 120, lines 156, 158 and 162, and orifice 160 toengage the clutch C2. Line 162 is also connected as an input toaccumulator 128, the backside of which is maintained at a regulatedpressure developed by valve 164. The engagement of clutch C2 is therebycushioned as the C2 apply pressure, resisted by spring force, strokesthe piston of accumulator 128. Of course, a 2-1 downshift is effected byenergizing the Solenoid Operated Valve A.

Referring again to the chart of FIG. 3, a 2-3 upshift is effected byenergizing Solenoid Operated Valve B to actuate the Shift Valve 124.This exhausts the clutch piston POC via orifice 166 to release theclutch OC, and supplies line pressure in line 66 to clutch piston P5 viaorifice 168 and line 170 to progressively engage clutch C5. Line 170 isconnected via line 172 as an input to accumulator 126, the backside ofwhich is maintained at a regulated pressure developed by valve 164. Theengagement of clutch C5 is thereby cushioned as the C5 apply pressure,resisted by spring force, strokes the piston of accumulator 126. Ofcourse, a 3-2, downshift is effected by deenergizing the SolenoidOperated Valve B.

Referring again to the chart of FIG. 3, a 3-4 upshift is effected bydeenergizing Solenoid Operated Valves B and C to return Shift Valves 124and 122 to their default positions, as depicted in FIGS. 1a-1b. TheShift Valve 124 thereby (1) exhausts clutch piston P5 and accumulator126 via line 170 and orifice 174 to release clutch C5, and (2) suppliespressure to clutch piston POC via lines 66 and 171 and orifice 176 toengage clutch OC. The Shift Valve 122 (1) exhausts clutch piston P4 vialine 152 and orifice 178 to release clutch C4, and (2) supplies DRpressure in line 132 to clutch piston P3 via Shift Valve 120, orifice180 and lines 182, 184, 73 and 140 to engage clutch C3. Line 182 isconnected via line 186 as an input to accumulator 130, the backside ofwhich is maintained at a regulated pressure developed by valve 164. Theengagement of clutch C3 is thereby cushioned as the C3 apply pressure,resisted by spring force, strokes the piston of accumulator 130. Ofcourse, a 4-3 downshift is effected by energizing the Solenoid OperatedValves B and C.

Referring again to the chart of FIG. 3, a 4-5 upshift is effected byenergizing Solenoid Operated Valve B to actuate the Shift Valve 124.This exhausts the clutch piston POC via orifice 166 to release theclutch OC, and supplies line pressure in line 66 to clutch piston P5 viaorifice 168 and line 170 to progressively engage clutch P5. As indicatedbelow, line 170 is also connected via line 172 as an input toaccumulator 126, which cushions the engagement of clutch C5 as the C5apply pressure, resisted by spring force, strokes the piston ofaccumulator 126. Of course, a 5-4 downshift is effected by deenergizingthe Solenoid Operated Valve B.

The Solenoid Operated Valves A, B and C, the TCC Bias Valve 108 and theLine Pressure Bias Valve 78 are all controlled by a computer-basedTransmission Control Unit (TCU) 190 via lines 192-196. As indicatedabove, the valves A, B and C require simple on/off controls, while thevalves 108 and 78 are pulse-width-modulated (PWM). The control iscarried out in response to a number of input signals, including anengine throttle signal %T on line 197, a turbine speed signal Nt on line198 and an output speed signal No on line 199. The throttle signal isbased on the position of engine throttle 16, as sensed by transducer T;the turbine speed signal is based on the speed of turbine shaft 42, assensed by sensor 200; and the output speed signal is based on the speedof output shaft 20, as sensed by sensor 202. In carrying out thecontrol, the TCU 190 executes a series of computer program instructions,represented by the flow diagrams of FIGS. 8, 9a-9b and 10-12 describedbelow.

As indicated above, shifting among the forward speed ratios iscoordinated through the use of Normal and Performance shift patternschedules, or look-up tables, which provide predefined threshold valuesfor comparison with measured vehicle parameters. In the illustratedembodiment, the Normal and Performance shift pattern look-up tablesstore upshift and downshift vehicle speed values for each ratio as afunction of the engine throttle position. If the measured vehicle speedexceeds the selected upshift speed value, an upshift to the next higherratio is initiated. If the measured vehicle speed falls below theselected downshift speed value, a downshift to the next lower ratio isinitiated. Normal and Performance look-up tables are also provided forthe control of transmission line pressure solenoid LP and the desiredshift times employed in adaptive pressure control.

Representative look-up tables for Normal and Performance modes aregraphically depicted in FIGS. 4a and 4b, respectively. In each case, theupshift speed values are designated as 1-2, 2-3, 3-4 and 4-5; thedownshift speed values are designated as 5-4, 4-3, 3-2 and 2-1. Notably,both upshift and downshift speed values are higher in the Performancemode than in the Normal mode. Consequently, the Performance mode tableoperates to extend operation in the lower speed ratios, compared to theNormal mode table. Similarly, the Performance mode line pressure tableprovides increased line pressure, compared to the Normal mode, toachieve a Performance shift feel. As also indicated above, thePerformance mode desired shift times, stored as a function of enginethrottle %T for each forward ratio, provide correspondingly reducedshift times to reflect the increased line pressure.

In conventional practice, a driver preference switch is employed toselect the appropriate shift pattern table--that is, Normal orPerformance. Alternately, some control logic may be employed to inferwhich table is most appropriate. Also, one or more intermediate shiftpattern tables have been employed to bridge the transition betweenNormal and Performance.

The objective of this invention is to provide a shift control system inwhich the parameters used to schedule the shift are dynamically andratiometrically adjusted between the predefined Normal and Performancelevels in response to an indication of the driving style of the operatorof the vehicle. When the driving style is relatively moderate orrestrained, transmission shifting is carried out using a set of normalor economy-oriented control parameters. When the driving style isrelatively extreme or unrestrained, transmission shifting is carried outusing a set of sport or performance-oriented control parameters. Whenthe operator's driving style is intermediate the two extremes,transmission shifting is carried out using a set of control parametersratioetrically intermediate the economy-oriented andperformance-oriented control parameters. The result is a shift controlparameter uniquely suited to the driving style of the operator of thevehicle.

In the illustrated embodiment, the indication of operator driving styleis based on a measure of the average peak acceleration of the vehicleduring operation in the lower forward speed ratios of transmission 14.To determine the indication of average peak acceleration, thelongitudinal acceleration of the vehicle is continuously determined inthe course of vehicle operation. The peak, or maximum, accelerationvalues occurring in successive ratio-dependent time intervals areidentified and accumulated to form cumulative and average peakacceleration terms, ACCSUM and AVPACC.

The ratio-dependency of the time intervals over which the peakacceleration values are identified causes a faster updating of theaverage peak acceleration AVPACC, and hence the shift controlparameters, in the lower ratios. This reflects an underlying recognitionthat the peak acceleration observed in the lower ratios provides a morereliable indication of the driver preference than that observed inhigher ratios. To this end, the acceleration time interval increaseswith increasing ratio, with little or no accumulation in the higherratios.

The above-described operation is graphically illustrated in FIG. 5,which depicts vehicle acceleration ACCEL over an extended time intervalinvolving successive 1-2, 2-3 and 3-4 upshifts, indicated below the timeaxis. The vertical reference lines intersecting the acceleration tracesubdivide the time scale into a series of successive time intervals, theduration of which varies with the current ratio. The time intervalsduring operation in second (2nd) gear are approximately twice as long asduring first (1st) gear, and the time intervals during operation inthird (3rd) gear are approximately twice as long as during second (2nd,)gear. The control unit 190 identifies the maximum or peak accelerationvalue MAXACCEL observed in each interval, as denoted by the dots on theacceleration trace in FIG. 5.

The peak acceleration values (MAXACCEL) are accumulated and averaged toform an average peak acceleration term, AVPACC. The average peakacceleration is then normalized, as shown in FIG. 7, to form a dynamicshift factor DSF. The dynamic shift factor is then used toratiometrically schedule the shift pattern, line pressure and desiredshift time between the predefined Normal and Performance values. Thisprovides a continuum of shift control parameters uniquely suited to thedriving style of the operator of the vehicle.

In the illustrated embodiment, a differential gain in the accumulationof the peak acceleration values is employed to bias the shift parameterschedules toward the Performance values. This is achieved byaccumulating peak acceleration values in excess of the average peakacceleration at a higher gain than peak acceleration values below theaverage peak acceleration. The effect of the differential gain isgraphically illustrated in FIG. 7, which depicts the average peakacceleration over an extended period of performance oriented t0-t1 andeconomy-oriented t1-t2 driving. With equivalent gains on accelerationand deceleration, the average acceleration term during economy-orienteddriving would follow the broken trace, quickly returning the control toeconomy-oriented (Normal) shift parameters. However, with thedifferential gain feature, the performance-oriented shift parameterscheduling is maintained over a longer period of time, as indicated bythe solid trace. This feature, combined with the ratio-dependency of thepeak acceleration time intervals, has been found to provide a shiftparameter schedule which closely satisfies driver expectations.

Referring now to FIGS. 8, 9a-9b and 10-12, the flow diagram of FIG. 8represents a main or executive computer program which is periodicallyexecuted in the course of vehicle operation in carrying out the controlof this invention. The blocks 230-232 designates a series of programinstructions executed at the initiation of each period of vehicleoperation for setting various terms and timer values to an initialcondition. Specific to the control of this invention, the block 232fetches an accumulated peak acceleration value ACCSUM from a previousperiod of vehicle operation, sets the number of acceleration samples#SAMPLES t one, clears the peak acceleration term MAXACCEL, andinitializes the acceleration interval timer (ACCEL TIMER) for the firstforward ratio. Thereafter, the blocks 234-254 are repeatedly executedduring the period of vehicle operation, as indicated by the flow diagramline 256.

First, the block 234 is executed to read the various inputs referencedin FIG. 1a. As detailed more fully in the flow diagram of FIGS. 9a-9b,the block 236 then computes the vehicle acceleration, ultimatelydetermining the value of a dynamic shift factor DSF. Then, the blocks238-240 determines the desired speed ratio Rdes and the torque converterclutch duty cycle TCC(DC). As detailed more fully in the flow diagram ofFIG. 10, the desired ratio Rdes is determined in relation to thecomparison of measured vehicle speed values with threshold speed valuesdetermined in relation to the engine throttle setting %T and the dynamicshift factor DSF. The torque converter clutch duty cycle TCC(DC) may bedetermined as a function of the throttle position, output speed No andthe difference between input and output speeds Ni and No.

If the actual ratio Ract--that is, Ni/No--not equal to the desired ratioRdes, as determined at block 242, the blocks 244-248 are executed toperform the appropriate logic for downshifting (block 246) or upshifting(block 248). In either event, the required shift solenoid state isdetermined as indicated at block 248. Additionally, in the case of anupshift, the throttle setting at the onset of the shift (% Tinit) isstored, and the percent of ratio completion (% RATCOMP) is computed.

In both shifting and nonshifting modes of operation, the blocks 250-254are then executed to determine the desired line pressure LPdes, toconvert the desired line pressure LPdes to a solenoid duty cycle LP(DC),to output the various duty cycles and discrete solenoid states to thesolenoid operated valves described above in reference to FIGS. 1a-1b,and to update the adaptive line pressure correction cells. Block 250 isset forth in further detail in the flow diagram of FIG. 11, and block254 is set forth in further detail in the flow diagram of FIG. 12.

Referring to the dynamic shift factor determination flow diagram ofFIGS. 9a-9b, the blocks 260 and 262 are first executed to decrement theacceleration interval timer ACCEL TIMER, and to calculate theacceleration ACCEL based on the change in output speed No since theprevious loop of the program. Blocks 264-266 identify the peakacceleration value by setting the term MAXACCEL equal to ACCEL wheneverACCEL exceeds the current value of MAXACCEL.

If the ACCEL TIMER has not yet been decremented to zero, as determinedat block 268, blocks 270 and 272 are executed to determine the averagepeak acceleration AVPACC and dynamic shift factor DSF based on theprevious accumulated peak acceleration value ACCSUM. At initialization,the accumulated peak acceleration value from a previous period ofoperation is used, as noted above in reference to block 232. Asindicated at block 272, the DSF determination may be a look-up table, asgraphically illustrated in FIG. 6.

At the expiration of each acceleration interval, the blocks 274-286 areexecuted to update the accumulated peak acceleration value ACCSUM. Atthe outset, the blocks 274 and 276 are executed to increment thebookkeeping term, #SAMPLES, corresponding to the number of accelerationintervals which have occurred in the current period of operation, and toreset the ACCEL TIMER to a new ratio-dependent value. In the illustratedembodiment, the ACCEL TIMER is initialized to approximately 0.5 sec infirst gear, 1.0 sec in second gear, 2.0 sec in third gear, and a verylong interval in fourth and fifth gears.

The block 278 then determines if various entry conditions are satisfied.These concern range selection, disengagement of the vehicle cruisecontrol system, minimum vehicle speed, converter slip and enginethrottle settings, service brake released and positive maximum peakacceleration MAXACCEL. If the conditions are not met, the accumulatedpeak acceleration value ACCSUM is not updated, and the block 280 isexecuted to clear the term MAXACCEL before continuing on to blocks270-272. If the conditions are met, the blocks 282-286 are executed toupdate the accumulated peak acceleration ACCSUM. If the peakacceleration MAXACCEL is greater than the average peak accelerationAVPACC, ACCSUM is updated according to the expression:

    ACCSUM=(ACCSUM+MAXACCEL)*[#SAMPLES/(#SAMPLES+1)]

If the peak acceleration MAXACCEL is less than or equal to the averagepeak acceleration AVPACC, ACCSUM is updated according to the expression:

    ACCSUM=[ACCSUM+MAXACCEL+K(AVPACC-MAXACCEL)]* [#SAMPLES/(#SAMPLES+1)]

In the case of lower than average peak acceleration, the addition of theterm K(AVPACC-MAXACCEL) partially offsets the reduced peak acceleration,effectively reducing the gain of accumulation for peak accelerationsless than or equal to the average peak acceleration AVPACC. As notedabove, this gives rise to the solid line characteristic depicted in FIG.7.

Referring now to the desired ratio determination flow diagram of FIG.10, the block 290 is first executed to look-up the upshift thresholdspeeds for the Performance and Normal modes, NVusp and NVusn. Asindicated in reference to FIGS. 4a-4b, the speed thresholds aredetermined by table look-up as a function of the engine throttle setting%T and the currently engaged speed ratio (GEAR). The block 292 thendefines an upshift speed threshold NVref according to the expression:

    NVref=NVusn+DSF(NVusp-NVusn)

This defines an upshift speed threshold ratiometrically spaced betweenthe Normal and Performance mode speed thresholds NVusn, NVusp by thenormalized dynamic shift factor DSF. If the vehicle speed Nv exceeds thereference NVref, as determined at block 294, the block 296 is executedto set the desired ratio Rdes to one ratio higher than the currentratio, GEAR.

Similarly, the blocks 298 and 300 are then executed to look-up thedownshift threshold speeds for the Performance and Normal modes, NVdspand NVdsn, and to define the downshift speed threshold NVref accordingto the expression:

    NVref=NVdsn+DSF(NVdsp-NVdsn)

This defines a downshift speed threshold ratiometrically spaced betweenthe Normal and Performance mode speed thresholds NVdsn, NVdsp by thenormalized dynamic shift factor DSF. If the vehicle speed Nv falls belowthe reference NVref, as determined at block 302, the block 304 isexecuted to set the desired ratio Rdes to one ratio lower than thecurrent ratio, GEAR.

Referring to the line pressure determination flow diagram of FIG. 11,the block 310 is first executed to look-up the desired line pressuresfor the Performance and Normal modes, LPn and LPp. As indicated above,the line pressure is typically determined by table look-up as a functionof vehicle speed Nv, engine throttle position %T, the currently engagedspeed ratio (GEAR), and any adaptive correction LPad determined duringprior upshifting. The adaptive correction values LPad are stored foreach gear as a function of engine throttle. The block 312 then definesthe desired line pressure LPdes according to the expression:

    LPdes=LPn+DSF(LPp-LPn)

This defines a desired line pressure which is ratiometrically spacedbetween the Normal an Performance mode pressures LPn, LPp by thenormalized dynamic shift factor DSF.

The Adaptive Update flow diagram of FIG. 12 determines the inertia phasetime of each normal upshift through the use of an inertia phase timer IPTIMER, compares the measured time to a reference time IPdes, and updatesthe adaptive pressure term LPad. If a single ratio upshift is inprogress, as determined at block 320, the blocks 322-330 are executed todetermine the shift time--that is, the time required to progress from20% ratio completion to 80% ratio completion. When %RATCOMP firstreaches 20%, as determined at block 322, the IP FLAG is set, and theblock 326 is executed to start the IP TIMER, and set the IP FLAG.Thereafter, block 324 will be answered in the negative, and when%RATCOMP reaches 80%, the blocks 330-340 are executed to stop the IPTIMER and complete the routine.

The blocks 332 and 334 operate to look-up the desired shift times IPn,IPp for the Normal and Performance modes, as a function of the initialthrottle position %Tinit and the desired speed ratio Rdes, and to definea desired shift time IPdes according to the expression:

    IPdes=IPp+DSF(IPn-IPp)

This defines a desired shift time for adaptive adjustment which isratiometrically spaced between the Normal and Performance mode shifttimes IPn, IPp by the normalized dynamic shift factor DSF.

The block 336 then determines the shift time error IPerror bydifferencing IPdes and the interval measured by IP TIMER. The block 338looks-up an adaptive line pressure modifier K as a function of thedetermined error IPerror and the currently engaged speed ratio, GEAR.Finally, the block updates the stored adaptive line pressure term LPadin accordance with the modifier K.

While this invention has been described in reference to the illustratedembodiment, it is expected that various modifications will occur tothose skilled in the art. For example, the operator driving styleindication may be based on various specified operating parameters of thevehicle, such as pedal movements, steering movements, engine load, etc.Moreover, various driver initiated overrides of the control could beprovided. In this regard, it should be realized that controlsincorporating such modifications may fall within the scope of thisinvention, which is defined by the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. In a motor vehicleadapted to be driven by an operator, including transmission gearelements defining a plurality of forward speed ratios and controlelements for shifting between speed ratios in response to predefinedshift control parameters, first look-up means for storing a first set ofshift control parameters for said control elements which set is suitedfor a normal driving style of said operator, and second look-up mans forstoring a second set of shift control parameters for said controlelements which is suited for a performance-oriented driving style ofsaid operator, a method of operation comprising the stepsof:periodically measuring specified operating parameters of said vehicleto form a dynamic shift control signal indicative of a current drivingstyle of said operator; obtaining a first shift control parameter formsaid first look-up means and a second shift control parameter form saidsecond look-up means; and ratiometrically determining a shift controlparameter for said control elements intermediate said first and secondshift control parameters based on said dynamic shift control signal,thereby to define a shift control parameter based on the driving styleof said operator.
 2. The method of operation set forth in claim 1,wherein said shift control parameter is a shift pattern value whichdetermines the initiation of shifting between said speed ratios.
 3. Themethod of operation set forth in claim 1, wherein said control elementsinclude fluid pressure operated elements, and said shift controlparameter represents a desired fluid pressure to be supplied to saidfluid pressure operated elements.
 4. The method of operation set forthin claim 1, wherein said dynamic shift control signal is normalized toform a dynamic shift factor which is applied to a difference betweensaid first and second shift control parameters in the determination ofsaid shift control parameter for said control elements.
 5. In a motorvehicle adapted to be driven by an operator, including transmission gearelements defining a plurality of forward speed ratios, a source of fluidpressure, and fluid pressure operated control elements for shiftingbetween speed ratios, first look-up means for storing a first desiredpressure to be supplied to said control elements by said source when anormal driving style is employed by said operator, and second look-upmeans for storing a second desired pressure to be supplied to saidcontrol elements by said source when a performance-oriented drivingstyle is employed by said operator, a method of operation comprising thesteps of:periodically measuring specified operating parameters of saidvehicle to form a dynamic shift control signal indicative of a currentdriving style of said operator; obtaining a first desired pressure formsaid first look-up means and a second desired pressure form said secondlook-up means; and ratiometrically determining a desired pressure to besupplied to said control elements by said source intermediate said firstand second desired pressures based on said dynamic shift control signal,thereby to define a desired pressure based on the driving style of saidoperator.
 6. The method of operation set forth in claim 5, where thevehicle includes third look-up means for storing a first desired shifttime for use in adaptively adjusting the pressure supplied to saidcontrol elements when a normal driving style is employed by saidoperator, and fourth look-up means for storing a second desired shifttime for use in adaptively adjusting the pressure supplied to saidcontrol elements when a performance-oriented driving style is employedby said operator, and the method of operation includes the stepsof:looking up first and second desired shift times from said third andfourth look-up means; and ratiometrically determining a desired shifttime intermediate said first and second desired shift times based onsaid dynamic sift control signal, thereby to define a desired pressurebased on the driving style of said operator.